An international team led by researchers at the Politecnico di Milano has devised a way to separate and distinguish optical beams even when the beams are superimposed, and even when the form in which the beams arrive at a destination is drastically changed and/or unknown. In the researchers’ design, the beams were separated in the optical domain and were simultaneously detected with negligible crosstalk — even when they shared the same wavelength and polarization. The phenomenon is enabled by a programmable photonic processor built on a 5-mm2 chip that receives all optical beams through microscopic optical antennas integrated onto the chip. A network of integrated interferometers manipulates the beams and separates them on distinct optical fibers, which eliminates interference. The device allowed information quantities of over 5000 GHz to be managed — a value that the research team said is at least 100× that which current high-capacity wireless systems can manage. “A peculiarity of our photonic processor is that it can self-configure very simply, without the need for complex control techniques,” said Francesco Morichetti, head of the Photonic Devices Lab at the Politecnico di Milano. “This allows scalability to new versions of the device, capable of handling many beams at the same time, further increasing the transmission capacity. It is also able to adapt in real time to compensate for effects introduced by moving obstacles or atmospheric turbulence, allowing the establishment and maintenance of optimal optical connections.” An international collaboration has developed a technique to separate and distinguish optical beams even if they are superimposed and the form in which they arrive at their destination is drastically changed and unknown. The development supports the ability to use on-chip designs in applications including precision positioning and self-driving cars. Courtesy of Politecnico di Milano. Like in optical fibers, light in free space can travel in beams that take different shapes, or modes, with each mode carrying a flow of information. The generation, manipulation, and reception of more modes means more the transmission of more information. However, free space is a more variable environment than an optical fiber, due to atmospheric agents that can alter the shape of light beams or otherwise affect them. The researchers identified applications that require the advanced processing of free space optics beams: wavefront sensing, phase-front mapping and reconstruction, multiple-beam transmission and imaging through scattering media, and chip-to-chip optical wireless communications. Additionally, high-precision positioning and localization systems, such as self-driving cars, and sensors, remote object detection, portable and wearable devices, and biomedical applications are among those that require the advanced processing of optical beams, the researchers said. Researchers from Stanford University, the Scuola Superiore Sant’Anna, and the University of Glasgow also participated. The research was published in Light: Science & Applications (www.doi.org/10.1038/s41377-022-00884-8).